초록 ▼

A compression-release brake system comprises an exhaust rocker arm, an actuation piston slidable in a piston bore in the exhaust rocker arm so as to press an exhaust valve, a supply conduit formed within the exhaust rocker arm, and an exhaust valve reset device mounted to the exhaust rocker arm. The

A compression-release brake system comprises an exhaust rocker arm, an actuation piston slidable in a piston bore in the exhaust rocker arm so as to press an exhaust valve, a supply conduit formed within the exhaust rocker arm, and an exhaust valve reset device mounted to the exhaust rocker arm. The actuation piston defines an actuation piston cavity within the actuation piston bore between the piston bore and the actuation piston. The exhaust valve reset device includes a reset check valve disposed between the supply conduit and the actuation piston cavity to hydraulically lock the actuation piston cavity by closing the reset check valve when a pressure of the hydraulic fluid within the actuation piston cavity exceeds the pressure of the hydraulic fluid in the supply conduit. The reset check valve is biased closed by the pressure of the hydraulic fluid within the actuation piston cavity during the brake-on mode.

대표청구항 ▼

1. A compression-release brake system for operating at least one exhaust valve of an internal combustion engine, said compression-release brake system operating in a brake-on mode during a compression-release engine braking operation and a brake-off mode during a positive power operation, said compr

1. A compression-release brake system for operating at least one exhaust valve of an internal combustion engine, said compression-release brake system operating in a brake-on mode during a compression-release engine braking operation and a brake-off mode during a positive power operation, said compression-release brake system maintaining said at least one exhaust valve open during a portion of a compression stroke of the engine when performing the compression-release engine braking operation, said compression-release brake system comprising: an exhaust rocker assembly for operating said at least one exhaust valve, said exhaust rocker assembly including an exhaust rocker arm mounted about a rocker shaft and selectively pivotable to open said at least one exhaust valve;an actuation piston moveable between retracted and extended positions and slidably disposed in an actuation piston bore formed in said exhaust rocker arm, said actuation piston operatively coupled to said at least one exhaust valve when in the extended position thereof;said actuation piston defining an actuation piston cavity within said actuation piston bore between said actuation piston bore and said actuation piston;a supply conduit formed within said exhaust rocker arm, said supply conduit configured to supply pressurized hydraulic fluid to said actuation piston cavity to displace said actuation piston to the extended position when there is a gap between said actuation piston and said at least one exhaust valve; andan exhaust valve reset device mounted to said exhaust rocker arm and including a reset check valve disposed between said supply conduit and said actuation piston cavity to hydraulically lock said actuation piston cavity by closing said reset check valve when a pressure of the hydraulic fluid within said actuation piston cavity exceeds the pressure of the hydraulic fluid in said supply conduit;said reset check valve biased closed by the pressure of the hydraulic fluid within said actuation piston cavity when operating in the brake-on mode during the compression stroke of the internal combustion engine;said reset check valve biased open by the pressure of the hydraulic fluid within said actuation piston cavity when operating in the brake-on mode during an expansion stroke of the internal combustion engine. 2. The compression-release brake system according to claim 1, comprising an exhaust valve bridge and first and second exhaust valves such that said exhaust rocker arm is selectively pivotable to open both said first and second exhaust valves through said exhaust valve bridge. 3. The compression-release brake system according to claim 2, wherein said actuation piston engages only said first exhaust valve in the extended position of said actuation piston. 4. The compression-release brake system according to claim 3, wherein said exhaust valve bridge has an opening such that a single-valve actuation pin is slidably movable relative to said exhaust valve bridge through said opening therein so that said actuation piston engages said first exhaust valve through said actuation pin. 5. The compression-release brake system according to claim 3, wherein said reset check valve is normally biased closed by a biasing spring. 6. The compression-release brake system according to claim 5, wherein said reset device further comprises a cartridge body mounted to said exhaust rocker arm and defining an inner cavity therewithin which houses said reset check valve; and wherein said inner cavity is fluidly connected with said continuous supply conduit and a high-pressure conduit that fluidly connects said inner cavity of said reset device with said actuation piston cavity. 7. The compression-release brake system according to claim 6, wherein said cartridge body is adjustably disposed within said exhaust rocker arm. 8. The compression-release brake system according to claim 6, wherein said cartridge body includes a continuous supply port fluidly connected to said continuous supply conduit and a piston supply port fluidly connected to said high-pressure conduit. 9. The compression-release brake system according to claim 8, wherein said inner cavity is fluidly connected with a brake-on supply conduit. 10. The compression-release brake system according to claim 9, wherein said cartridge body further includes a brake-on supply port fluidly connected to said brake-on supply conduit. 11. The compression-release brake system according to claim 10, wherein said reset check valve is disposed between said supply conduit and said high-pressure conduit to selectively control fluid communication therebetween; and wherein said high-pressure conduit provided between said actuation piston cavity and said reset check valve. 12. The compression-release brake system according to claim 11, wherein said cartridge body of said reset device is non-moveable relative to said exhaust rocker arm during compression-release engine braking operation. 13. The compression-release brake system according to claim 12, wherein said reset device further comprises a reset trigger extending from said exhaust rocker arm; and wherein said reset trigger has an elongated distal end at least partially extending from said cartridge body toward said exhaust valve bridge and is movable relative to said cartridge body between an extended position and a retracted position. 14. The compression-release brake system according to claim 13, wherein said reset trigger is normally biased to the retracted position by a trigger return spring. 15. The compression-release brake system according to claim 14, wherein said exhaust valve reset device further comprises an upset pin extending between said reset trigger and said reset check valve for opening said reset check valve when said reset trigger is in the retracted position. 16. The compression-release brake system according to claim 15, wherein said cartridge body is provided with a contacting foot swivelably mounted to a distal end thereof adjacent to said exhaust valve bridge. 17. The compression-release brake system according to claim 16, wherein said reset trigger extends from said contacting foot through an opening therein. 18. The compression-release brake system according to claim 6, further comprising a compression release actuator operatively coupled to said reset device. 19. The compression-release brake system according to claim 18, wherein said compression release actuator comprises a casing non-movable relative to said rocker shaft and a brake-on piston reciprocating within said casing; wherein said brake-on piston defines a brake-on piston cavity within said casing; and wherein said casing includes a fluid port open to said brake-on piston cavity and connected with a source of pressurized fluid. 20. The compression-release brake system according to claim 19, wherein said casing is provided with a piston stroke limiting pin that limits upward and downward movement of said brake-on piston. 21. The compression-release brake system according to claim 20, wherein said brake-on piston has an axially extending groove receiving said piston stroke limiting pin therein. 22. The compression-release brake system according to claim 19, wherein said cartridge body of said reset device is moveable relative to said exhaust rocker arm during compression-release engine braking operation. 23. The compression-release brake system according to claim 4, further comprising a compression release actuator operatively coupled to said reset device. 24. The compression-release brake system according to claim 23, wherein said compression release actuator comprises a casing non-movable relative to said rocker shaft and a brake-on piston reciprocating within said casing; wherein said brake-on piston defines a brake-on piston cavity within said casing; and wherein said casing includes a fluid port open to said brake-on piston cavity and connected with a source of pressurized fluid. 25. The compression-release brake system according to claim 24, wherein said reset check valve is disposed in said brake-on piston. 26. The compression-release brake system according to claim 25, wherein said reset check valve is normally biased open by a biasing spring. 27. The compression-release brake system according to claim 26, wherein said exhaust valve reset device further includes a rocker check valve disposed in said exhaust rocker arm outside said actuation piston so that said actuation piston cavity is disposed between said rocker check valve and said reset check valve. 28. The compression-release brake system according to claim 27, wherein said rocker check valve is disposed between said actuation piston cavity and said supply conduit. 29. The compression-release brake system according to claim 27, wherein said actuation piston has a communication conduit fluidly connected with said piston cavity through said reset check valve; and wherein said communication conduit in said actuation piston is fluidly connected directly to said supply conduit. 30. The compression-release brake system according to claim 1, wherein the exhaust rocker arm includes a contacting foot facing and selectively engaging an exhaust valve bridge and spaced therefrom by a predetermined valve lash when said exhaust rocker arm is not acting on said exhaust rocker arm. 31. The compression-release brake system according to claim 1, wherein the actuation piston bore is formed at a distal end of said exhaust rocker arm. 32. A method of operation of a compression-release brake system in a brake-on mode for operating at least one exhaust valve of an internal combustion engine during a compression-release engine braking operation, said compression-release brake system maintaining said at least one exhaust valve open during a portion of a compression stroke of the engine when performing the compression-release engine braking operation, said compression-release brake system comprising: an exhaust rocker assembly for operating said at least one exhaust valve, said exhaust rocker assembly including an exhaust rocker arm mounted about a rocker shaft and selectively pivotable to open said at least one exhaust valve;an actuation piston moveable between retracted and extended positions and slidably disposed in an actuation piston bore formed in said exhaust rocker arm, said actuation piston operatively coupled to said at least one exhaust valve when in the extended position;said actuation piston defining an actuation piston cavity within said actuation piston bore between said actuation piston bore and said actuation piston;a supply conduit formed within said exhaust rocker arm, said supply conduit configured to supply pressurized hydraulic fluid to said actuation piston cavity to displace said actuation piston to the extended position when there is a gap between said actuation piston and said at least one exhaust valve; andan exhaust valve reset device mounted to said exhaust rocker arm and including a reset check valve disposed between said supply conduit and said actuation piston cavity to hydraulically lock said actuation piston cavity by closing said reset check valve when a pressure of the hydraulic fluid within said actuation piston cavity exceeds the pressure of the hydraulic fluid in said supply conduit;said method comprising the steps of:mechanically biasing said reset check valve closed during a first part of a valve brake lift of said at least one exhaust valve during a compression stroke of the internal combustion engine;hydraulically biasing said reset check valve closed during a second part of a valve brake lift of said at least one exhaust valve following the first part during the compression stroke; andresetting said at least one exhaust valve during an expansion stroke of the engine by opening said reset check valve and releasing hydraulic fluid from said actuation piston cavity to close said at least one exhaust valve. 33. The compression-release brake system according to claim 32, wherein said reset check valve is opened due to the decreased pressure of the hydraulic fluid in said actuation piston cavity during the expansion stroke of the internal combustion engine. 34. The compression-release brake system according to claim 32, comprising an exhaust valve bridge and first and second exhaust valves such that said exhaust rocker arm is selectively pivotable to open both said first and second exhaust valves through said exhaust valve bridge. 35. The compression-release brake system according to claim 34, wherein said actuation piston engages only said first exhaust valve in said extended position of said actuation piston. 36. The compression-release brake system according to claim 35, wherein said reset check valve is normally biased closed by a biasing spring; and wherein said reset check valve is mechanically biased closed by said biasing spring during said first half of said valve brake lift of said first exhaust valve during the compression stroke of the internal combustion engine.